diff -r 8aaf187d25f0 -r e45d2890749d progs/lecture1.scala
--- a/progs/lecture1.scala	Mon Nov 09 17:49:12 2020 +0000
+++ b/progs/lecture1.scala	Sat Nov 14 00:40:47 2020 +0000
@@ -2,16 +2,19 @@
 //=================
 
 
+
 // Value assignments
 // (their names should be lower case)
 //====================================
 
+
 val x = 42
 val y = 3 + 4 
 val z = x / y
 val x = 70
 print(z)
 
+
 // (you cannot reassign values: z = 9 will give an error)
 //var z = 9
 //z = 10
@@ -292,26 +295,29 @@
 // For-Comprehensions (not For-Loops)
 //====================================
 
-(1 to 10).toList
-for (n <- (1 to 10).toList) yield { 
-  square(n) + 1
+val lst = (1 to 10).toList
+for (n <- lst) yield n * n 
+
+
+for (n <- lst) yield { 
+  square(n) + double(n)
 }
 
 for (n <- (1 to 10).toList; 
-     m <- (1 to 10).toList) yield (m, n)
+     m <- (1 to 5).toList) yield (n, m, n * m)
 
 
 // you can assign the result of a for-comprehension
 // to a value
 val mult_table = 
   for (n <- (1 to 10).toList; 
-       m <- (1 to 10).toList) yield m * n
+       m <- (1 to 10).toList) yield n * m
 
 println(mult_table.mkString)
 mult_table.sliding(10,10).mkString("\n")
 
-// the list/set/... can also be constructed in any 
-// other way
+// for-comprehensions also work for other
+// collections
 
 for (n <- Set(10,12,4,5,7,8,10)) yield n * n
 
@@ -319,17 +325,14 @@
   n * n  
 }
 
-if (1 == 2) "a" else "b"
+// with if-predicates / filters
 
-// with if-predicates / filters
+if (1 == 2) "a" else "b"
 
 for (n <- (1 to 3).toList; 
      m <- (1 to 3).toList;
      if (n + m) % 2 == 0) yield (n, m)
 
-for (n <- (1 to 3).toList; 
-     m <- (1 to 3).toList;
-     if ((((n + m) % 2 == 0)))) yield (n, m)
 
 // with patterns
 
@@ -343,11 +346,31 @@
 // general pattern of for-yield 
 // (yield can be several lines)
 
-for (p <- ...) yield {
+for (pat <- ...) yield {
   // potentially complicated
   // calculation of a result
 }
 
+// For without yield
+//===================
+
+// with only a side-effect (no list is produced),
+// has no "yield"
+
+for (n <- (1 to 10).toList) println(n * n)
+
+for (n <- (1 to 10).toList) yield n * n
+
+// BTW: a roundabout way of printing out a list, say
+val lst = ('a' to 'm').toList
+
+for (i <- (0 until lst.length)) println(lst(i))
+
+// Why not just? Why making your life so complicated?
+for (c <- lst) println(c)
+
+
+
 // Functions producing multiple outputs
 //======================================
 
@@ -371,23 +394,6 @@
 strs.maxBy(_._1)
 
 
-// For without yield
-//===================
-
-// with only a side-effect (no list is produced),
-// has no "yield"
-
-for (n <- (1 to 10)) println(n)
-
-(1 to 10).toList
-(1 until 10).toList
-// BTW: a roundabout way of printing out a list, say
-val lst = ('a' to 'm').toList
-
-for (i <- (0 until lst.length)) println(lst(i))
-
-// Why not just? Why making your life so complicated?
-for (c <- lst) println(c)